The present invention relates to a printer head of, for example, an inkjet printer and to an electrostatic actuator applicable to such a printer head.
A conventional inkjet printer ejects ink droplets on paper by driving a heater element or a piezoelectric element to print an image. Japanese Unexamined Patent Application Publication No. 10-315466, for example, discloses such a method in which the driving is performed by an electrostatic actuator.
FIG. 1 is a cross-sectional view of the printer head having the electrostatic actuator. The printer head 1 includes a predetermined substrate 2 whose surface has recesses formed thereon at a given pitch. Each recess has an electrode 3 on the bottom thereof. The printer head 1 also includes a component 5 having bottom plates 6 and partitions of ink liquid cells 4 on the substrate 2. The component 5 formed of a conductive material is disposed over the electrodes 3. The electrodes 3 disposed on the substrate 2 face the bottom plates 6 of the respective ink liquid cells with the distance therebetween being defined by the recesses of the substrate 2 so that the component 5 is insulated from the electrodes 3. The bottom plates 6 of the component 5 have a predetermined thickness so as to function as a diaphragm. Another component 8 having nozzles 7 is disposed over the component 5.
In this printer head 1 having the above-mentioned structure, when a voltage is applied to the space between the component 5 and one of the electrodes 3, the corresponding bottom plate 6 is attracted and bent towards the electrode 3. When the application of the voltage is stopped, the bottom plate 6 is restored to its original state. Accordingly, the application of the voltage generates an electrostatic force between the electrode 3 and the component 5 to change the volume in the ink liquid cell 4 of the printer head 1. The pressure generated by the decreased volume of the ink liquid cell 4 ejects ink from one of the nozzles 7.
An inkjet printer having a heater element requires large electric power for driving the heater element. Thus, the entire unit consumes a large amount of power. On the other hand, an inkjet printer having a piezoelectric element has difficulties with the integration of the piezoelectric elements, leading to a complicated manufacturing process. For these reasons, various kinds of methods have been presented to solve these problems and also to improve the level of performance in inkjet printers having the heater element or the piezoelectric element.
In contrast to the inkjet printer having the heater element or the piezoelectric element, the printer head having the electrostatic actuator still has possibilities for further improvements and may solve the problems residing in the inkjet printer having the heater element or the piezoelectric element.
As mentioned above, in the conventional printer head having the electrostatic actuator, the component 5 having the bottom plates 6 and the partitions of the ink liquid cells 4 and the component 8 having nozzles 7 are stacked on the substrate 2 in that order. This assembly process, however, is complicated. This process also impairs the precision in the positioning of the component 5 and the component 8, and may cause ink leakage among the substrate 2, the component 5, and the component 8. Because the component 5 is disposed on the substrate 2, the connecting faces of the substrate 2 and the component 5 must be planarized. This causes problems with integration of a driving circuit of the electrostatic actuator on the substrate 2.